1. Field of the Invention
This invention relates to a modified polybenzimidazole, a method for preparing the same, an electrode made from a polybenzimidazole compound, and a method for detecting hydrogen peroxide using the electrode.
2. Description of the Related Art
Polybenzimidazoles, characterized by great chemical stability, high thermal resistance, high mechanical strength, etc., are well known to be suitable for use in a separatory media, such as a filtration film or an ion exchange resin. The most serious problem for polybenzimidazoles is that they are soluble only in a solvent with high polarity, such as dimethylsulfoxide, N,N-dimethylacetamide, N,N-dimethylformamide, and N-methylpyrrolidinone. At present, methods for improving solubility of polybenzimidazoles include, e.g., introducing a flexible side chain or modifying the main chain structure of polybenzimidazoles.
U.S. Pat. No. 4,814,400 discloses novel polybenzimidazole esters, polybenzimidazole carboxylic acids, and methods for producing both. The methods include reacting polybenzimidazole polymers with halogenated alkyl esters to form polybenzimidazole esters and subsequently hydrolyzing the polybenzimidazole esters to form polybenzimidazole carboxylic acids. The polybenzimidazole esters and the polybenzimidazole carboxylic acids thus produced have a repeating unit represented by the following formula:
wherein T1 is a tetravalent aromatic group, T2 is arylene or alkylene, T3 is a C1 to C22 alkylene group, and T4 is hydrogen, a C1 to C20 alkylene group, a C1 to C20 alkenylene group, or a C1 to C20 arylene group.
In this U.S. patent, the method for producing polybenzimidazole carboxylic acid is a two-step procedure, which is complicated, and the solubility of the polybenzimidazole esters and the polybenzimidazole carboxylic acids are never addressed.
Therefore, there is a need in the art to provide a polybenzimidazole derivative having good solubility, and a relatively simple method for producing the same.
In the method for detecting hydrogen peroxide by virtue of an electrochemical device, an electrode used in the electrochemical device can be classified into enzyme electrode and non-enzyme electrode. An electrochemical device using an enzyme electrode has the advantage of superior specificity, but the stability and activity of the enzyme would be easily influenced by the environment and the duration of use. As to an electrochemical device using a non-enzyme electrode, an oxidation potential is usually measured in this device to determine the amount of hydrogen peroxide. Since the oxidation potential is susceptible to interference with other undesired substances in a test sample, the specificity for hydrogen peroxide is reduced and the accuracy of the test result would be adversely affected.
An electrode used for detecting hydrogen peroxide disclosed in U.S. Pat. No. 5,320,725 includes a testing surface and a transducing film covering the testing surface. The transducing film includes a cross-linked redox polymer network having a redox compound and a peroxidase chemically bonded to the redox polymer network. The method for detecting hydrogen peroxide disclosed in this patent includes: oxidizing peroxidase by virtue of hydrogen peroxide; reducing the oxidized peroxidase by oxidizing the redox compound of the redox polymer network; electroreducing the oxidized redox compound by electrons originated at the electrode; and measuring a generated current. Because the peroxidase of the transducing film is an enzyme, the electrode of this patent is not stable and is easily influenced by the environment, and the life span of the electrode is limited.
Therefore, there is a need in the art to provide an electrode for an electrochemical device which has good stability and high specificity for hydrogen peroxide.